Acute toxicity and environmental risk of diflubenzuron to Daphnia magna, Poecilia reticulata and Lemna minor in the absence and presence of sediment

Parasitoses in fi sh farming are treated by the application of pesticides formulations commonly used in agriculture or veterinary medicine. For the control of ectoparasites, that cause economic losses to the fi sh production Difl ubenzuron is utilized by direct application into water at a 2 mg.L-1 concentration. However, this practice can intoxicate nontarget species. This research aimed at determining the acute toxicity of difl ubenzuron to Daphnia magna, Poecilia reticulata and Lemna minor; evaluating its environmental risk and defi ning the role of the sediment in the bioavailability of this insecticide in the water. Results of the study implicate difl ubenzuron as being extremely toxic to D. magna. However, no signifi cant toxicity was observed in P. reticulata and L. minor. Bioavailability of this insecticide was signifi cantly reduced by the presence of sediment in the water.

Swimbladder abnormalities in piapara (Leporinus obtusidens) captured downstream of the Funil Dam

Fish damage in hydroelectric stations has been extensively reported, but further investigations focusing on Brazilian migratory species, especially large fish, are needed. The present study describes swimbladder abnormalities in piapara Leporinus obtusidens, a migratory physoclistous species, collected downstream from the Funil Hydroelectric station dam, Minas Gerais, Brazil. The 117 specimens collected were dissected for swimbladder evaluation in the coelomic cavity. The abnormalities detected in 14 of the fish (12 percent) were swimbladder rupture with exteriorization (N = 12) and formation of sac-like projections (N = 2). The specimens that had swimbladder abnormalities weighed over 1300 g for both sexes. These abnormalities may be caused by bladder infections, however, inflammation process were not detected in these fish. The presence of anomalies in swimbladder suggests that the individuals were subjected to sudden depressurization, possibly related to passage through the turbines. Further comparative studies are needed to corroborate this hypothesis.

Os danos que as usinas hidrelétricas causam na fauna aquática tem sido relatados, mas novos estudos focando as espécies nativas, especialmente os peixes de grande porte são necessários. O presente estudo descreve as anomalias de bexiga natatória em piapara Leporinus obtusidens, uma espécie de peixe migratório, coletados a jusante da barragem da estação Hidrelétrica do Funil, Minas Gerais, Brasil. Os 117 exemplares coletados foram dissecados para avaliação da bexiga natatória na cavidade celomática. As anormalidades detectadas em 14 dos peixes capturados (12 por cento) foram ruptura do tecido com exteriorização da bexiga natatória (N = 12) e formação de projeções da bexiga (N = 2). Os exemplares que apresentavam anormalidades de bexiga, possuíam peso superior a 1300 g em ambos os sexos. Este tipo de anomalia pode ser causado por processo infeccioso da bexiga, no entanto, não foram detectados processos inflamatórios nesses peixes. O quadro de anomalias em bexiga natatória em piapara sugere que os indivíduos foram submetidos a uma brusca despressurização, possivelmente relacionada à passagem pelas turbinas. Outros estudos comparativos são necessários para corroborar esta hipótese.